The only thing that's medically necessary is 4 menstrual cycles per year (that's why there is a birth control pill that allows you to skip your period for 3 months at a time). So, no, you won't have any adverse side-effects from delaying menstruation for short periods of time.

Medications for delaying periods work on the hormones that regulate your menstrual cycle and should not be taken without prescription. Before taking any medication for delaying your periods, I would strongly suggest you to consult with your gynecologist who would take into account other factors like medicines that you are taking, your current health condition and so on in order to prescribe you a suitable medicine for delaying your periods.

Long term health effects of these medicines is not well known yet and like all medicines these can also show side effects. Delaying periods for major events once in a while is ok, but it should not be made into a common practice.

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